The present invention relates generally to the construction of freight moving vehicles and, more particularly, to a railway car having a lowered center of gravity.
Over the years, railway cars have progressed from relatively simple general purpose wooden structures mounted on flat cars to more elaborate arrangements including insulated walls, refrigeration equipment, nailable metal floors, and other features for specific applications. Various types of railway cars are presently manufactured and used. A typical railway freight car includes an enclosed structure mounted on a railway car underframe. The enclosed structure may include an outer shell and interior paneling. For some railway freight cars, such as refrigerated box cars, one or more layers of insulation may be disposed between the outer shell and the interior paneling.
The outer shell of a railway freight car often has an exterior surface formed from various types of metal such as steel or aluminum alloys. The interior paneling is often formed from wood and/or metal as desired for the specific application. Sliding doors are generally provided on each side of the enclosed structure for loading and unloading freight. Conventional railway freight cars may be assembled from various pieces of wood, steel and/or sheets of composite material such as fiberglass reinforced plastic and generally require significant amounts of raw material, labor and time to complete manufacture and assembly of each freight car.
The underframe for many railway freight cars includes a center sill with a pair of end sills and a pair of side sills arranged in a rectangular configuration corresponding approximately with the dimensions for the floor of the freight car. Cross bearers and cross ties are often provided to establish the desired rigidity and strength for transmission of vertical loads to the center sill. A plurality of longitudinal stringers are typically provided on each side of the center sill to support the floor of the enclosed structure. Examples of such railway car underframes are shown in U.S. Pat. Nos. 2,783,718 and 3,266,441. Both of these patents are incorporated by reference for all purposes within this application.
In the United States, the Association of American Railroads (AAR) controls the guidelines with which railway car manufacturers must comply when designing and building railway cars. The AAR guidelines dictate such design parameters as maximum lengths, widths, weights as well as many others.
In the interest of safety, the Association of American Railroads (AAR) has also established guidelines regarding the way in which railway cars may be loaded. One such guideline concerns the combined center of gravity of a railway car and its load. In this combined center of gravity guideline, the combined center of gravity of a railway car and its load is not to exceed ninety-eight inches (98xe2x80x3) above the top of the rail. In general, when a shipping agent loads a railway car with lading for transportation, the shipping agent is required to calculate the combined center of gravity of the railway car and its contents whenever any part of the load exceeds one hundred forty inches (140xe2x80x3) or eleven-feet and eight-inches (11xe2x80x28xe2x80x3) in height above the car floor.
The combined center of gravity of a railcar and its load may be defined as follows:
Combined Center of Gravity                               Combined  Center  of  Gravity  (          CG          )                =                              [                                          (                                  B                  xc3x97                  E                                )                            +                              (                                  D                  xc3x97                  F                                )                                      ]                                (                          E              +              F                        )                                              Eq.  1            
In equation 1, xe2x80x98Axe2x80x99 is the measure of the height of the car floor above the top of the rail; xe2x80x98Bxe2x80x99 is the center of gravity of the railcar when empty, xe2x80x98Cxe2x80x99 is the center of gravity of the load above the car floor, xe2x80x98Dxe2x80x99 is the height of the center of gravity of the load above the top of the rail and is equal to the sum of xe2x80x98Axe2x80x99 and xe2x80x98C,xe2x80x99 xe2x80x98Exe2x80x99 is the unloaded weight of the railcar and xe2x80x98Fxe2x80x99 is the weight of the load.
As a result of the AAR guidelines regarding combined center of gravity height limitations, a shipping agent may be unable to use the full capacity of a given railway car when shipping certain ladings. For example, a paper mill wishing to ship rolls of paper may be unable to use the full capacity of a boxcar having a seventeen foot interior height without violating the AAR combined center of gravity guidelines. As such, many shipping agents are forced to resort to other methods of shipping such as trucking, to ship their goods in an economical manner.
To overcome the load limits resulting from the combined center of gravity limitations in the AAR guidelines, various methods have been attempted. One method for lowering the center of gravity on a railway car is commonly called ballasting. Ballasting of a railway car involves hanging a number of weights from one or more side sill channels on the railway car as close to the rails or railway tracks as possible to achieve as much lowering of the combined center of gravity as possible. One of the drawbacks of ballasting is the loss of load limit that results from having to add significant amounts of ballasting weight to achieve an appreciable lowering in the railway car""s center of gravity.
In accordance with teachings of the present invention, a railway car underframe having a lowered center of gravity is provided. The railway car underframe of the present invention preferably includes a pair of end sills cooperating with a pair of side sills to form a generally rectangular configuration and a plurality of cross bearers extending between the side sills and spaced laterally from each other between the end sills. The underframe preferably also includes a center sill extending between the end sills along a center line of the rectangular configuration and disposed above at least one of the plurality of cross bearers. A pair of coupler assemblies disposed on respective ends of the rectangular configuration and a pair of railway trucks disposed at respective ends of the generally rectangular configuration proximate the end sills are also preferably included in the railway car underframe. A body bolster extending between the center sill and the side sills above each of the railway trucks and a bolster plate extending between the side sills above each of the body bolsters may also be included in the railway car underframe. A plurality of wheel pans extending from each body bolster and sized to extend over each wheel of the railway trucks are also preferably included in the railway car underframe having a lowered center of gravity of the present invention.
In an another embodiment, a railway car having first and second end sills disposed generally normal proximate respective ends of first and second side sills to form a generally rectangular configuration is provided. The railway car preferably includes a center sill disposed along a longitudinal center line of the rectangular configuration and a plurality of cross bearers extending between the side sills and spaced laterally from each other between the end sills. A pair of railway trucks disposed proximate the first and second end sills along with a body bolster extending between the center sill and the first and second side sills above each of the respective railway trucks are also preferably included. The railway car may include a bolster plate disposed above each body bolster and extending between the side sills and a plurality of wheel pans attached to and extending horizontally from each body bolster and sized to extend over the respective railway trucks. To form a part of the railway car""s flooring, a plurality of floor stringers extending between the first and second end sills and the wheel pans and spaced laterally from each other between the center sill and the first and second side sills and a plurality of floor stringers extending longitudinally between the wheel pans above the respective railway trucks and spaced laterally from each other between the center sill and the first and second side sills, where the plurality of floor stringers disposed on at least one cross bearer, are also preferably included. As part of the railway car""s flooring surface, a plurality of nailable metal floor planks extending between the center sill and the first and second side sills and spaced laterally from each other between the first and second end sills is provided. A pair of coupler assemblies disposed proximate the first and second end sills are also preferably included.
In a further embodiment, a railway car having a lowered center of gravity is provided. The railway car preferably includes a pair of end sills cooperating with a pair of side sills to form a generally rectangular configuration. A plurality of cross bearers extending between the side sills and spaced laterally from each other between the end sills is also preferably included. A center sill extending between the end sills on a longitudinal center line of the rectangular configuration and disposed on one or more of the plurality of cross bearers and a plurality of floor stringers extending between the end sills and spaced laterally from each other between the center sill and the side sills may also be included. One or more of the plurality of floor stringers are preferably disposed on one or more of the plurality of cross bearers. The railway car may further include a floor system disposed on the plurality of floor stringers and a pair of railway trucks disposed proximate each end sill. In addition, a body bolster extending between the center sill and the side sills above each of the railway trucks, a bolster plate disposed above each body bolster and extending between at least the center sill and the side sills and a plurality of wheel pans attached to and extending horizontally from each body bolster with the wheel pans sized to extend over the respective railway trucks are also preferably included in the railway car having a lowered center of gravity provided by the present invention.
One technical advantage of the present invention includes the ability to increase the amount of low density and/or lightweight lading that can be carried by a railway car without violating AAR center of gravity guidelines.
Another technical advantage of the present invention includes the lowering of a railway car""s center of gravity without reducing the railway car""s freight capacity.
An additional technical advantage of the present invention includes a modified railway car operable to accommodate various types of lading as well as loading configurations.